The present invention relates to fabricating crystalline silicon microelectronic components, particularly to forming thin-film single-crystal silicon on insulator substrates, and more particularly to a method for fabricating thin-film single-crystal silicon on insulator substrates using electroless etching for achieving efficient etch stopping on epitaxial silicon substrates.
Single-crystal silicon in insulator substrates has been previously proposed as a solution to the problems facing the flat-panel display industry. Such prior efforts are exemplified by U.S. Pat. No. 5,399,231 issued Mar. 21, 1995; No. 5,414,276 issued May 9, 1995; and No. 5,674,758 issued Oct. 7, 1997, as well as copending application Ser. No. 08/871,709 filed Jun. 9, 1997, entitled xe2x80x9cSilicon on Insulator Achieved Using Electrochemical Etchingxe2x80x9d, assigned to the same assignee. These prior approaches to the above-referenced problems used strain dependent etch stops such as heavily boron doped silicon, SiGe:B, and SiGe layers. These provide excellent resistance to the etching of KOH and permit very fine control of the final silicon thin film thickness. The disadvantage of using these layers is that they are expensive and not commercially viable solutions to thinning wafers.
The present invention provides a solution to the above-referenced problems and takes advantage of the existing silicon substrates used in silicon fabrication facilities. Thus, there is no burden placed on the semiconductor manufacturer to take advantage of the method of the present invention. The method of this invention uses electroless etching for achieving efficient etch stopping on epitaxial silicon substrates for fabricating thin-film single-crystal silicon on insulator substrates. There are various applications for the substrate-thinned circuits produced by this method, including flat-panel displays.
It is an object of the present invention to provide a method for fabricating thin-film single-crystal silicon on insulator substrates.
A further object of the invention is to provide a fabrication method involving electroless epitaxial etching for producing substrate-thinned circuits.
Another object of the invention is to provide a method for producing microelectronic circuits and devices which utilize electroless etching for achieving efficient etch stopping on epitaxial silicon substrates.
Another object of the invention is to provide an improvement in the fabrication of thin-film single-crystal on insulator substrates using electroless etching for achieving efficient etch stopping on epitaxial silicon substrates.
Another object of the invention is to provide a fabrication method wherein microelectronic circuits and devices are prepared on epitaxial silicon wafers, the wafers are bonded to a holding substrate, the silicon bulk is removed using electroless etching leaving the circuits and devices contained within the epitaxial layer remaining on the holding substrate, and defining streets and wire bond pad areas for electrical access to the circuit via a photolithographic procedure.
Other objects and advantages of the present invention will become apparent from the following description and accompanying drawings. The present invention basically involves electroless epitaxial etching for semiconductor applications. More specifically, the present invention involves a method for fabricating thin-film single-crystal silicon on insulator substrates using electroless etching for achieving efficient etch stopping on epitaxial silicon substrates. The method of this invention eliminates the burden and expense previously used to form the etch stops, and provides a commercially viable solution to thinning wafers. After microelectronic circuits and devices are prepared on epitaxial silicon wafers in a standard fabrication facility, and the wafers are bonded to a holding substrate, the silicon bulk is removed using electroless etching leaving the circuits and devices contained within the epitaxial layer remaining on the holding substrate, and thereafter, via a photolithographic process, streets and wire bond pad areas are defined for electrical access to the circuit. The end product being substrate-thinned circuits produced by a commercially viable method which places no extra burden on the semiconductor manufacturer.